An Unconventional Reef

Note: This is an article - quite critical of Wet/Dry Filtration - that I wrote shortly after the mini-reef craze hit America, but never had the guts to send in for publication.

It's an old joke:

Percy comes home from the pet shop with a beautiful parrot named Fred. But try as he might, Percy just can't get Fred to talk, so he returns to the pet shop for advice. "Won't talk, eh?", the clerk says (with an outlandish accent, if you're any kind of storyteller at all), rubbing his hands together. "Probably bored; the secret is to get a few of these special toys." So Percy goes home with an armload of parrot playthings and assembles them all in Fred's cage. But still not a peep from Fred. As time goes on, Percy acquires a bigger cage, a companion "Fred-ette", a color television, and a mobile home - all to no avail. Finally, a weary and penniless Percy shouts (rhetorically, if you don't mind), "I just don't understand. I've gone to enormous lengths and spared no expense to provide you with all the luxuries of parrot life; I've quit my job and broken my wedding engagement to have more time to spend with you. And still, you haven't seen fit to utter even a single syllable on my behalf! What more could you possibly want?!" Fred, apparently impressed with his benefactor's great soliloquy if not his generosity, sidles slowly over nearer poor Percy, and in a hoarse, cracking voice, says, "Bird food, you idiot!", and falls, stone dead, from his perch.

Many of us seem to exhibit the "Percy syndrome" when it comes to caring for our marine aquariums. In an effort to provide the best environment for our little slice of the sea, we often veer off on a tangent seeking the "secret" of success, and overlook the many factors that combine to create a healthy aquarium. At the risk of being branded a heretic, I would like to suggest that this is much the case with the current wave of reef-mania.

Before we go any further, I would like to point out that I maintain three reef-type aquaria at the aquarium shop that I manage: one commercial model, one home-made, and a third, rather unconventional system that I will detail a bit later. Each has been successful to some extent, so I am not writing out of inexperience, nor do I have any axe to grind with any of the systems. I am also excited about the possibilities the future has in store for us, influenced chiefly by the enthusiasm of reef hobbyists. On the other hand, I have found that much of the "gospel" of reef tanks - particularly concerning wet/dry filtration - just doesn't seem to hold water.

When wet/dry filters were re-introduced two years ago (I saw very similar systems a dozen or so years ago), I'll have to admit, I was already a bit skeptical. The claim that they were used for years by "everybody" in Europe sounded good on the surface, but I've heard the same claim about fast-flow canisters, slow-flow canisters, undergravel filters and no filters. Since I've never been to Europe, I will have to assume that various hobbyists use various filters, just as we do here. In addition, it seemed that most people that praised wet/dry filtration either had little or no experience with them or were selling them - or both. Finally, some of the claims of these systems just didn't seem to make sense.

The Weakest Link Theory. I'm sure everyone has heard the age-old bit of wisdom: "A chain is only as strong as its weakest link.", but few of us seem to apply it to aquarium theory. In essence, the weakest link theory tells us that, when we consider all the factors, success depends on whichever factors are least fulfilled. Strengthening the already-strong links will not increase success unless the weak links are also strengthened. Even though Fred (remember Fred?) had all the luxuries of parrot life, he could not survive unless his weakest link, food, was provided for.

Biological Filtration. Ever since Stephen Spotte's landmark book, Fish and Invertebrate Culture, aquarists worldwide have recognized the importance of biological filtration in elimination of ammonium and nitrite ions. What we have failed to recognize, however, is that Biological Filtration is not onlt essential, it's nearly unavoidable! It seems that anywhere there is circulating, aerated water and nitrogenous waste to feed upon, our "friendly" bacteria are happy to move in. It does not seem necessary to go to great lengths to culture these bacteria to keep ammonia and nitrite levels down. In other words, biological filtration does not seem to be the weakest link in the reef-keeping chain. In the vast majority of our store marine aquariums, we use no form of undergravel or other recognized biological filtration. And yet, it is very rare to test even a trace of ammonia or nitrite in any of them, in spite of relatively crowded, overfed conditions. In fact, the only problems we've ever been able to tie to ammonia or nitrite conditions occured in undergravel filtered tanks in which air pumps or power heads failed, which seemed to be an all too common event.

It does not seem sensible to assume that we can improve upon biological filtration with wet/dry or undergravel filters. Since all the ammonia and nitrite is consumed by bacteria, even in a tank without wet/dry, it is logical to think of this food source as being the bacteria's weakest link. If this is the case, then no extra circulation, aeration, or surface area will permanently increase the number of active bacteria in the aquarium. Any excess bacteria produced would put a strain on the ammonia/nitrite food source, and equilibrium would be achieved when enough bacteria had either died or become dormant.

Mechanical and Chemical Filtration. My biggest concern about wet/dry filters is that, for the most part, they ignore two of the three forms of filtration. In order to build a super efficient biological filter, chemical and especially mechanical filtration are often sacrificed. Since most reef systems skim water from the surface of the aquarium, any uneaten food or solid waste never enters the filter system until after it decays and dissolves. Whatever solid waste makes it into the wet/dry filter threatens to smother the biological filter bed. Fortunately, some wet/dry manufacturers now include a prefilter to help prevent this from occuring, although gravity fed mechanical filters have a tendency to plug quickly and either slow down or overflow the system.

What About Nitrates? Contrary to some information I've seen, few commercial reef systems seem to include any sort of nitrate removal systems. Nitrate reduction can only occur in oxygen-depleted water, which of course is the exact opposite of what wet/dry filters are trying to achieve. Separate "denitrator" units are available, but results are inconsistent at best. Most reef tanks rely on lush growths of macro algae to control nitrates.

That Third Tank. A while back I mentioned a third reef tank at our store - one that utilized an unconventional (for a reef system) filter system. This is a ninety gallon (48"L x 18"W x 24"H) all glass aquarium with a Lifegard mechanical module powered by a 600 gallon per hour pump. The only adaptation made on this unit was to use a much larger intake strainer basket to prevent wayward anemones from choking the system. I might add a spray bar to the output in the future to provide more uniform circulation. Two six-inch airstones are employed at opposite ends of the aquarium and approximately one inch of crushed coral covers the bare tank bottom. Four 48" fluorescent bulbs - two 40 watt actinic and two 40 watt daylight bulbs provide the lighting. (If there is a "secret of success" to reef tanks, it's the lighting.) That's it - no wet/dry, no undergravel filter.

It is by far our most trouble-free reef tank. The superior mechanical filtration provided by the Lifegard keeps the water crystal clear and the gravel clean. As I said before, we have never had an ammonia or nitrite problem in this tank. Since the solid waste is removed from the system regularly before it has a chance to break down, dissolved organics do not accumulate so quickly. The specimens of hard and soft corals, anemones and live rock thrive. All of the most expensive or unusual pieces go in this tank as do any specimens that are stubborn about opening up.

Wet/dry filters are not necessarily without value, but there are other options. I hope that many other hobbyists will give reef tanks with canister filters a try, and that they will share in our success.